Wheel rims for various type aircraft may include a rim body having an integral inboardly positioned tire bead flange, a demountable outboardly positioned tire bead flange, a split lockring seated within an annular radial groove in the rim body and, a means associated with the lockring to maintain it on the wheel rim. In wheel rim assemblies of this type, a deflated tire is firstly mounted on the rim body and it is followed by the demountable bead flange which is moved inboardly on the rim body such that the split lockring may be seated within the annular groove provided for it proximate the outboard edge of the rim body. Upon inflation of a mounted tire, the demountable bead flange is moved outboardly on the rim and into forceful engagement with the split lockring. Alternatively, when the tire is to be demounted from the rim, it is firstly deflated and the demountable bead flange is moved inboardly to disengage the lockring. The split lockring may then be removed from within its mounting groove and the demountable bead flange and deflated tire removed from the rim body in the outboardly direction.
It is well-known in the industry that, in the particular circumstance of a tire blowout when traveling at a high rate of speed, the outboardly positioned tire bead tends to work inboardly on the rim and this allows the demountable bead flange to follow in the same direction. In this situation, a forceful engagement as between the flange and lockring is lost and the lockring is subject to being thrown off of the rim body by the high centrifugal forces which are present. As these type wheel rims are used for aircraft applications, the above-described situation of tire blowout creates a very serious hazard to aircraft operations. Solutions to the problem of lockring throw-off are disclosed in the prior art as exemplified in U.S. Pat. Nos. 4,635,695 and 4,683,930 wherein various type wire devices are applied to the split lockring to maintain it on the rim body when forceful engagement with the demountable bead flange is lost.
It should be made clear that, with respect to the prior art patents referenced above, the split lockring is termed a "retaining ring" inasmuch as that is the manner that these have been catalogued by various agencies. The terminology "retaining ring", however, is found to be used generally and generically for a wide range of split ring fasteners as these are known and used in the mechanical arts. In view of this, the terminology "retaining ring" will not be used in this specification for the split rings of the type which are used for securing a demountable tire bead flange on a wheel rim body. The terminology "split lockring" will be used hereinafter for such wheel rim lockrings and the terminology "retaining ring" will only be used to refer to any of the various type spring metal split rings as these are known and used in the fastening arts.
To continue, there is a particular aircraft application known in the industry as "high floatation tire application" wherein somewhat lower tire pressures are used. In this type application, the wheels of the landing gear are subjected to changing forces imposed by varying runway surfaces during taxi runs and turns as well as during takeoffs and landings. These varying forces result in tire pressure variations which act on the bead flanges of the wheel rim. It has been found that such pressure variations effect minute physical movements at the flange-lockring joint and this results in fretting action within the lockring mounting groove in the rim body. The fretting can result in cracks in the rim body which, while easily detected in a normal inspection, result in an early retirement of the wheel rim.
It is, therefore, in accordance with one aspect of the present invention an object to provide a demountable bead flange and split lockring assembly configuration which does not produce fretting within the lockring groove in the wheel rim body.
In accordance with another aspect of the invention it is an object to provide a configuration for a demountable bead flange and split lockring assembly wherein engagement between the two is characterized by a wedge-locking load force at the joint such as to eliminate any relative movement of the split lockring within its mounting groove.
According to another aspect of the present invention it is an object to provide a configuration for a demountable bead flange and split lockring assembly wherein the bore of the flange transitions into a chamfer at its outboard end and the split lockring has an outer surface chamfer which matches the chamfer in the flange bore such that a compressive wedge-locking force exists between the two at the joint in the normal operation of the wheel rim.
In accordance with still another aspect of the invention it is an object to provide a demountable bead flange and split lockring assembly for a wheel rim characterized by bevelled interfacing surfaces of the flange bore and lockring surface which define an angle of not more than 30.degree. with reference to an axis of the rim.
According to another aspect of the present invention it is an object to provide an improved configuration for a wheel rim demountable bead flange and split lockring assembly wherein a split retaining ring cooperates in combination with the assembly to effect a self-locking and pre-loaded annular joint between the members which maintains a wedge-lockup of the members.